Products by Four Roses Bourbon:

Company email (October 2017)
"The neck wrap that we use for our single barrel is NOT real leather. It is 100% synthetic. According to your website, this has caused us to be classified as non-vegan. As a brand that uses no animal products in our Bourbon or processes, I believe we qualify to be categorized as vegan."

Company email:
"The closest thing to animal we have in our products is the yeast that we use to ferment our grains...and I'm sure that doesn't count. So to answer your question, no
there are no animal ingredients either in the product or used in any part of the processing in the US, Europe, Japan, or anywhere else in the world."